Tool for processing drilled holes

ABSTRACT

A tool for processing holes has a shaft which can be clamped in a drive element for executing a forward stroke into a working position within a hole, a return stroke, and an at least rotating working motion of the tool, two support elements arranged on the shaft, wires clamped at one end of the shaft between the support elements and being sprung bowing away from the shaft in an arc shape, the wires being coated with a cutting medium. One of the support elements is axially adjustable relative to the shaft. The shaft has axially positioned slots distributed on a circumference in two regions axially offset from one another. The shaft also has an axial hole leading out from both ends of the shaft and extending into the regions. The support elements are formed as limit stops inserted in the axial hole and each end just short of an entry of the hole into an area of the slots. The wires have ends extending through the slots and coming to rest on the limit stops.

BACKGROUND OF THE INVENTION

The present invention relates to a tool for processing drilled holes.

More particularly, it relates to a tool which has a shaft which can beclamped into a drive element which serves to execute a forward stroke ofthe tool into a working position within the hole, a return stroke, andan at least rotating working motion of the tool, wires clamped at oneend of the shaft between two support elements on the shaft and beingsprung bowing away from the shaft in an arc shape and coated with acutting medium, with one of the support elements is axially adjustablerelative to the shaft.

In a tool of this type, two sleeves are fitted on a solid shaft; thesesleeves surround the shaft, at a distance from one another, and intothem are inserted, between shaft and sleeve, on the side facing eachother, a large number of wires which are supported with their ends onthe sleeves, are tensioned in an arc shape, and are coated with acutting agent. The wires lie very close together, so that they fill outthe whole circumference around the shaft and cannot be displaced towardsone another in the circumferential direction at the support point. Oneof the sleeves can be axially adjusted relative to the shaft by means ofa screw thread, so that the wires can be prestressed to a greater orlesser extent, producing more or less bowing-out from the shaft. Thetool is inserted into the holes to be treated, and can then be used, forexample, to remove particles of material protruding from a transversehole into the drilled hole, by a rotating motion. Due to the necessaryclose coverage with wires over the circumference, the tool is relativelyrigid, but can process drilled holes of different diameters only withina narrow tolerance range. In order to prevent the wires from beingtwisted or pulled out, the direction of drive must be continuouslyreversed during the processing. Moreover, as the tool is relativelylarge it is not possible to go below a lower diameter range of the holeto be treated. For technical and production reasons, this diameter is 8mm in the known tool. One disadvantage is that replacing the wires inthe case of damage, or when the cutting agent coating has been worn off,necessitates, the replacement of all the wires, even if some of themcould still be usable.

Such tools, and other tools, are used for ultra-fine and most closelytoleranced after-treatment of holes, in particular, in those cases wherethere are also transverse holes breaking into the drilled holes. Initems of this nature, after the completion of a longitudinal hole intowhich, for example, a pump plunger of a fuel injection pump will laterhave to operate under very high pressures of e.g. 1,000 bar, and aftercompletion of the transverse holes leading into this longitudinal hole,the longitudinal hole is microfinished by honing after the workpiece hasbeen hardened. Following such processes burrs regularly occur, whichprotrude into the transverse hole and would lead to faults in theoperation of the fuel injection pump. These burrs must be removed. Thiscan be achieved with a burring tool, such as is known from DE-OS3333499. This is effected by inserting a deburring tool from the outsidethrough the transverse hole which removes the burrs at the junctionbetween the transverse hole and the longitudinal hole. A further problemexists in that the breakthrough of the transverse hole into thelongitudinal hole is not in a flat plane, so that the deburring toolremoves varying amounts of material from different areas of thecircumference; thus the desired sharp-edged transition from transversehole to longitudinal hole is not ensured. This deburring also has theresult that, in turn, a residue of burrs protrudes into the longitudinalhole. This would result in causing the high-precision pump plunger toseize in the longitudinal hole. For this reason, the remaining burrsmust subsequently be removed, once again, without detriment the surfaceof the finished honed longitudinal hole. This removal of the residualburr, or of burrs which protrude into a hole in general, can be effectedby means of a tool in accordance with the state of technology mentionedabove, or else round brushes are used whose external circumference isaccurately matched to the diameter of the longitudinal hole and whichhas nylon bristles with a cutting agent added. These round brushes havea diameter which is accurately matched to the diameter of thelongitudinal hole, and when they are used for the first time they mustbe clamped over a defined length and aligned to prevent running out oftrue. A further disadvantage is that the brushes have only a relativelyshort life, since due to wear, the diameter reduction is possible onlyin a very narrow range. Brush material being welded on to the wall ofthe longitudinal hole can also occur. Subsequent cleaning of thelongitudinal hole in turn means increased expense. If the round brushesare used with cutting oil, then such deposits are avoided, but theefficiency of the bristles is diminished due to lower rigidity withreducing contact pressure. Furthermore, for each drilled hole diameter,an matched brush must be used, so that in the machines providing theprocessing, different workpiece diameters present a problem.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a toolof the above mentioned general type, which avoids the disadvantages ofthe prior art.

In keeping with these objects and with others which will become apparenthereinafter, one feature of the present invention resides, brieflystated, in a tool, in which the shaft has axially positioned slotsdistributed on the circumference in two regions axially offset from oneanother, as well as an axial hole leading out of both ends of the shaft,preferably two blind holes, which both extend into the regions and towhich limit stops are inserted as support elements, with each stopending in the hole just short of its entry into the area of the slots,and on which the ends of the wire fed through the slots come to rest.

When the tool is designed in accordance with the present invention, itoffers the advantage that holes of different diameters can be simply andprecisely processed, with practically consistent results being achieved,even when dealing with relatively large diameter variations. Moreover,the tool can also be used successfully for hole diameters smaller than 8mm. Once a tool has been chucked, workpieces of different diameter holescan be processed. The tool has a long tool and the wires coated with thecutting medium can be quickly and simply replaced. The number of coatedwires required to equip a tool is relatively small. As a result,stock-keeping for the wear parts of the tool is simple and economical,and repair times are short. The wires are held securely in the slots,and with their preloading or bowing, they can be simply and accuratelyadjusted to match different hole diameters. Since the coating of thewires consists of the same or similar material as that of the strips ofhoning tools, the high processing quality achieved in the longitudinalhole before the final deburring is maintained. Due to the targetedprecise contacting of the wires on the surface of the hole, theprocessing time is short in comparison with processing with brushes. Thetool can be used both with cutting oil or dry. Due to the flexibility ofthe wires, conical, longitudinally elliptical, or offset holes can beprocessed.

In accordance with an advantageous embodiment of the present invention,a compression spring is held between one limit stop formed as a pin anda bolt which adjusts the pin, and the bolt is adjustable in direction ofthe spring until it comes to rest on a shoulder. This embodimentprovides, in an advantageous manner, for an almost constant contactpressure of the wires on the wall of the hole to be achieved, since thelimit stop can be moved against the compression spring, and thecompression spring essentially determines the radial force component onthe wall of the hole. Further, this contact pressure can be individuallyvaried when selecting the compression spring, via the spring constant.

In accordance with still a further embodiment of the present invention,the bolt is designed as a stud, and the compression spring is supportedon the pin and/or stud via a hardened ball. In this embodiment thecondition is achieved whereby, with any adjustment of the pin on whichthe wires are supported, a rotational motion is transmitted to the pinvia the stud, and thus the ends of the wires are not restrained withinthe slots, but remain freely movable. The embodiment in accordance withclaim 6 ensures that the slots are not closed by the pin moving into theregion of the slots, and that the ends of the wires can thus be easilyinserted.

In accordance with another embodiment of the present invention, thecoating of the wires with cutting medium is provided in the middleregion, but no further than just short of the entry of the wires intothe slots. This embodiment achieves the condition that the slots aresubjected to the minimum wear by the movement of the wires on insertionand removal of the tool, so that long and satisfactory operation of thewires is guaranteed. This can also ensure that the entering edge of thehole to be treated is not subjected to excessive stock removal duringthe insertion procedure. Until the final form of the wires, matched tothe hole, has been achieved, these wires slide past the opening of thehole with their uncoated portions. Only in the final state do the coatedparts of the wires rest on the wall of the hole.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional view of the tool in accordance with thisinvention, and

FIG. 2 shows the tool in use, within the hole to be processed.

DESCRIPTION OF PREFERRED EMBODIMENTS

The tool for processing holes, shown in longitudinal section in FIG. 1,has a shaft 1, which in this example is designed as a subdivided shaftwith a front shaft part 2 on the workpiece side. This shaft part has aconstant external diameter, and is set into a second shaft part 3 on thefront end. The shaft part 3 has a locating shaft 4, via which it can beinserted in a chuck, not shown here, of a drive element. The locatingshaft 4 leads into a intermediate piece 5 with a smaller diameter, intowhich, as mentioned above, the shaft part 2 is inserted on the frontend.

The shaft has a first blind hole 7, which is formed coaxially to theaxis of shaft part 2 on the front end of the shaft part's workpieceside. Further, the shaft has a second coaxial blind hole 8 which isdesigned as a stepped hole with a stepped hole portion 10 of a largerdiameter, located in the region of the locating shaft. This stepped holeportion, forming a shoulder 11, leads into a stepped hole portion 12 ofa smaller diameter, with this stepped hole portion extending in theregion of the intermediate piece 5 and there subsequently into shaftpart 2.

On the shaft part 2 a first area 14, is provided in which slots 15 areevenly arranged, parallel to the axis, on the circumference of the shaftpart 2; these converge into the first blind hole 7 over their entirelength. Furthermore, on the shaft part 2, at an axial distance from thefirst area 14, a second area 16 is provided in which slots 15, alsodistributed around the circumference, are provided. They are axiallylimited and over their entire length converge into the stepped holeportion 12 with the smaller diameter, within the shaft part 2.Advantageously, the number of slots is an even multiple, so that twoslots always lie diametrically opposite one another, which simplifiesmanufacture. The first blind hole 7 is closed on the front end by astopper or a screwed part 18, which extends to just before the start ofthe slots and is there equipped, on its front end, with a tappet 19. Inthe embodiment example in question, the stopper 18 is firmly connectedwith the shaft part 2.

Inserted into the second blind hole 8 is a pin 21, which has a head 22towards the locating shaft. The head slides inside the larger diameterstepped hole portion 10, and can be brought to rest against the shoulder11. In this position, the end of the pin 21 is located just short of thestart of the slots 15 on the locating shaft, so that these cannot beclosed by the pin 21. On the front end, the pin 21 also has a tappet 24.On the head 22 of the pin is a hardened ball 25; held between this and athreaded bolt 27, which is screwed into an internal screw thread 26 ofthe stepped hole portion 10, is a compression spring 29. On the endprotruding from the stepped hole portion 10 on the front end, thethreaded bolt has a knurled head 31, with which the threaded bolt can bescrewed in and out, and which does not exceed the external diameter ofthe locating shaft. Between the knurled head 31 and the front end 32 ofthe locating shaft, a lock nut 33 is screwed onto the stud, to fix itsposition or depth. Other options of securing are possible. The ball 25prevents rotation being transmitted to the pin 21 when adjusting thethreaded bolt 27, which otherwise could lead to the wires jamming in theslots. Between the tappet 24 on the pin 21 and its externalcircumference, a ring shoulder 34 is formed as a support surface. Thering shoulder should preferably consist of low-wear, hardened material,and the ends of sprung wires 36, fed through the slots 15, should cometo rest against it. With its ring shoulder 34, the pin 21 serves as asupport element at one end of these wires. At the other end, the wires36 are fed through slots 15 of the first area 14, and come to rest on aring shoulder 37, preferably also of hardened material, between tappet19 and stopper 19. Together with the tappet 18, this ring shoulder formsa second support element. Since the distance between ring shoulder 34and ring shoulder 37 is less than the length of the wires, these arebowed away from the shaft 2, and in the starting shape they have a bowedform. The wires are brought at least in the region of their insertionthrough the slots. The width of the slots is adapted to the diameter ofthe wires, so that these can be led in precise axial alignment. Theprovision of the tappet 24 or 19, prevents the ends of the wires fromcrossing over each other; in fact, they have a defined resting point inthe immediate vicinity at the tappet. Clear of the slots, the wires arecoated with a cutting medium, which for preference is of diamond grit,in a manner similar to that for cutting medium for honing strips. Othercutting media in use with honing strips are equally suitable for wirecoating. The coating 38 on the wires preferably extends only in a middleregion symmetrically to the centre portion of the bow formed by thewires in the starting condition. This results in an uncoated insertionregion 39, which is located towards the end of the shaft part 2. Inorder to provide this insertion region, it would also be sufficient ifthe wires were coated, not symmetrically, but coated only on one side.However, it is simpler and safer for installation if a particularfitting position does not have to be observed when installing the wires.

The bowing of the wires 36 can be varied by the position of the supportelements being changed relative to each other, by the stud 27 beingscrewed in or out.

Accordingly, the wires bow out to a greater or lesser extent. Thus thetool can be adapted to different hole diameters to be processed. In FIG.2, the tool is shown inserted. The shaft part 2 was fed into alongitudinal hole 43, which had previously been microfinished by, fore.g. honing, by the feed of the drive element. A transverse hole 44,breaks into this longitudinal hole 43, of which the entering edge intothe longitudinal hole 43 had previously been processed by, for e.g. adeburring tool, or which in general, on its entering edge has burrsprotruding into the longitudinal hole 43. When the tool is inserted withthe shaft part 3, the wires slide past the entering edge 45 of thelongitudinal hole with their insertion regions 39 into the hole, and indoing so they are distorted in such a way that they then take on theshape shown in FIG. 2. Here, the wires rest with their coated part onthe wall of the drilled hole, parallel to the axis, along generatinglines of the longitudinal hole 43. Due to the fact that the wires canmove together with the pin 21 against the force of the spring 29 in alongitudinal direction, it is ensured that there is an even contactpressure of the wires against the wall of the longitudinal hole 43.During the working motion of the tool which follows the forward stroke,and which may occur as a rotary movement, or a movement in only onedirection, and which can also be effected to harmonise with the workingmotion of honing tools, the burrs at the transition from the transversehole 44 to the longitudinal hole 43, is removed by the coating of thewires, without the surface quality of the longitudinal hole beingadversely affected. In order to achieve a contact pressure of the wireswithin the longitudinal hole, it is necessary that the external diameterof the wires 36, in the state shown in FIG. 1, is greater than thediameter of the longitudinal hole 43. For preference, the differenceshould be a factor of 1.8. Thus an optimum length of the wires isbrought to rest in the longitudinal hole. After processing thelongitudinal hole 43 of the workpiece 46, the tool is withdrawn.

The tool can be used with a multiple-spindle honing machine in which theworkpieces are automatically fed. It is also possible to processworkpieces with longitudinal holes of differing diameters. By adjustingthe free clamping length between the shoulders 34 and 37, in addition tothe general diameter tolerances for the holes, holes of larger diameterscan also be processed, e.g. within the range of 6 to 9 mm.

As an alternative to the described embodiment, the free clamping lengthof the wires can also be varied from the front end of the shaft part 2,if a setting pin is provided from this end. The setting of theembodiment shown in FIG. 1 could also be effected with an adjusting partof a different design, instead of by means of a stud. It is thenadvantageous to match the adjustment to that provided for honing tools.

With the tool as described, a multitude of processing options isoffered, with it being possible to process not only cylindrical drilledholes but also drilled holes of other forms, since the wires adaptthemselves according to the surface. At the end of their useful life,the wires can be easily removed from the tool. The head 22 resting onthe shoulder 11 prevents the slots 15 being covered by the pin 21,making the insertion of new wires more difficult. Advantageously, it ispossible to replace individual wires which show severe wear, this beingeasily effected due to the given distribution around the circumference.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied in atool for processing drilled holes, it is not intended to be limited tothe details shown, since various modifications and structural changesmay be made without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:
 1. A tool for processing holes,comprising a shaft which can be clamped in a drive element for executinga forward stroke into a working position within a hole, a return stroke,and an at least rotating working motion of the tool; two supportelements arranged on the shaft; wires clamped at one end of the shaftbetween said support elements and being sprung bowing away from saidshaft in an arc shape, said wires being coated with a cutting medium,one of said support elements being axially adjustable relative to saidshaft, said shaft having axially positioned slots distributed on acircumference in two regions axially offset from one another, said shaftalso having an axial hole leading out from both ends of said shaft andextending into said regions, said support elements being formed as limitstops inserted in said axial hole and each ending just short of an entryof said hole into an area of said slots, said wires having endsextending through said slots and coming to rest on said limit stops. 2.A tool for processing holes as defined in claim 1, wherein said axialhole is formed by two blind holes.
 3. A tool for processing holes asdefined in claim 1, wherein one of said limit stops is formed as a pinwhich is adjustable from outside.
 4. A tool for processing holes asdefined in claim 3; and further comprising a bolt which can beintroduced from said one end of said shaft and adjust said pin.
 5. Atool for processing holes as defined in claim 4; and further comprisinga compression spring located between said bolt and said pin, said boltbeing adjustable in the direction of said spring.
 6. A tool forprocessing holes as defined in claim 5; and further comprising ashoulder against which said bolt comes to rest after being adjusted inthe direction of said spring.
 7. A tool for processing holes as definedin claim 4, wherein said bolt is formed as a stud.
 8. A tool forprocessing holes as defined in claim 7, wherein said compression springis supported on at least one of said pin and said stud via a hardenedball.
 9. A tool for processing holes as defined in claim 8, wherein saidcompression spring is supported on said pin and on said stud via ahardened ball.
 10. A tool for processing holes as defined in claim 6,wherein said axial hole has a larger diameter blind hole and a smallerdiameter blind hole, said pin having a head at an end of said spring,said head sliding in said larger diameter blind hole, said pin having anadjustment path which is limited in direction towards said wires by saidhead resting against said shoulder, said shoulder being formed at atransition between said larger diameter blind hole and said smallerdiameter blind hole.
 11. A tool for processing holes as defined in claim4, wherein said ball is formed as a stud provided with an knurled headlocated outside and having a locking element to secure the position ofsaid stud.
 12. A tool for processing holes as defined in claim 11,wherein said locking element is a locknut.
 13. A tool for processingholes as defined in claim 1, wherein said limit stops have a tappet on aside facing said wires; and further comprising a further shoulder formedbetween said tappet and said limit stop so that said end of said wirescomes to rest on said shoulder.
 14. A tool for processing holes asdefined in claim 1, wherein said cutting medium is provided in a middleregion of said wires but no further than just short of an entry of saidwires into said slots.
 15. A tool for processing holes as defined inclaim 1, wherein said cutting medium is a diamond grid embedded in acarrier agent.